A bicycle frame comprises components such as down tube, top tube, head tube, seat tube, chain stay and seat stay, which are also designated frame components. The bicycle frame may be configured in one piece or, for example in the case of fully suspended bicycles, comprise a joint which rotatably interconnects the various frame components. Components for the purposes of the following print are not only frame components, however, but also components intended for mounting on such a bicycle frame, for example handlebars or a part of handlebars, for example a handlebar cross-brace, a seat post or a front fork or parts thereof such as the fork legs. The bicycle frame can be intended for bicycles with different purposes, such as a competition bicycle, a racing bicycle, a time trial bicycle, a mountain bike, an electric bicycle or a pedelec.
Such components are supporting components which fulfill a supporting function on the bicycle frame. For this purpose, such components must meet certain strength requirements, in particular with regard to flexural, buckling and torsional stiffness. For example, flexural stiffness depends on the square moment of inertia of the component into which there enters the cube of the dimension of the component in whose direction the flexural stiffness is being viewed. The strength requirements thus determine the minimum dimensions of the component, such as width and depth. If the component must have for example a higher strength perpendicular to the travel direction than in the travel direction of the bicycle, the resulting component having the minimum dimensions corresponding to the strength requirements has a greater dimension perpendicular to the travel direction than in the travel direction. Such a component has a low weight, but it possesses only low aerodynamic efficiency. For example, down tubes with a width of 52 mm and a depth of 46 mm are known.
For improving aerodynamic efficiency it is known to configure components in the form of wing profiles. Such wing profiles have been standardized by NACA (National Advisory Committee for Aeronautics) and are completely described for example by four-digit code numbers. Such wing profiles are employed in asymmetrical configuration as airplane wings. For use in bicycle frames there play a role substantially only symmetrical wing profiles which have no camber. Hence, the first two code numbers of four-digit NACA profiles are zero. The last two code numbers describe the profile thickness as a percentage of the profile depth, i.e. the maximum width of the profile based on the length of the chord line connecting the leading edge to the trailing edge. The rearward point of maximum thickness in four-digit NACA profiles is 30%, i.e. the maximum width of the profile is at 30% of the profile depth measured from the leading edge along the chord line. Such wing profiles are often employed for the down tube, the seat tube and the head tube of time trial bicycles.
Further, the International Cycling Union (Union Cycliste Internationale, UCI) regulates the configuration of components for frames of bicycles which may be used for competitive purposes. For example, such a component may not exceed a maximum depth of 80 mm. Likewise, such a component must have a minimum width of 25 mm. For seat stays, chain stays and fork legs the minimum width is 10 mm. Further, the ratio of depth to width of a tube may not exceed 3:1. In other words, the minimum width of a frame component is one third of its depth.
In view of the regulations of the International Cycling Union, there can thus be used for components within the meaning of the present print wing profiles with a relative profile thickness, based on the profile depth, of more than 33.3%, as is fulfilled for example by the NACA profile 0034 or four-digit NACA profiles with even higher values of the last two code numbers.
If there is located immediately behind a component a further bicycle part, it is further known to provide the component as a wing profile with a considerably smaller relative profile thickness, for example a NACA profile 0020, in which a part of the back area is absent. Because of the thereby reduced profile depth, such a component can also be configured according to the regulations of the International Cycling Union. Such a configuration of a frame component is known for example for the seat tube to which the back wheel is immediately adjacent. Additionally, the back of the seat tube can be configured concavely, so that the seat tube partly receives the back wheel.
However, the use of a complete wing profile as a cross section for a frame component increases the production cost because of the very small radius occurring on the profile trailing edge. Further, the alternative structure of the frame component with an absent back area improves the aerodynamic efficiency over a complete wing profile only when there is adjacent immediately therebehind a further bicycle part, for example the above-described back wheel.